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OIL SEPARATOR.- The oil separator is located downstream of the compressor and check valve. It operates on a centrifugal principle; that is, the oil mist refrigerant enters the inlet port of the separator at a tangent to the wall of the cylindrical housing. This imparts a swirling or centrifugal action to the mixture. The centrifugal force has a greater effect on the heavier oil vapors, causing them to collect on the walls and the conical screen. The oil drips from the screen and collects at the bottom of the oil separator. Oil flows from the bottom of the separator through an oil flow indicator and filter and is injected into the compressor at the shaft seal cavity. The refrigerant vapor rises through the tubular baffle and leaves the separator. A circular sight gauge is provided on the separator to check the level of system oil during operation. Normal oil level is a half full sight gauge.
OIL FLOW INDICATOR.- The oil flow indicator in the oil return line is basically a metal cage with a sight window. It is used to observe the amount of oil returning to the compressor and to prevent compressor failure when no flow is indicated. OIL FILTER.- Oil returning to the com-pressor passes through a filter, which ensures a clean oil supply for compressor lubrication. The filter has a replaceable cellulose fiber element. If the filter becomes clogged, a bypass device permits unfiltered oil to circulate through the compressor when the differential pressure across the filter is greater than 18 to 22 psi. When the differential pressure across the filter is greater than 13.5 to 16.5 psi, the red indicator at the top of the filter will pop up and remain extended to provide an indication that the filter requires replacement prior to becoming completely clogged, and consequently passing contaminant oil to the compressor. The oil filter is designed with an automatic shutoff feature, which permits removal of the filter element and bowl without loss of the refrigerant charge. CONDENSER EJECTOR AIR SHUTOFF VALVE.- The purpose of the condenser ejector air shutoff valve is to increase airflow across the condenser during ground operation by discharging engine bleed air through the ejector assembly. The valve is pneumatically operated. It is controlled by a piston through a mechanical linkage and is spring loaded to the CLOSED position. A solenoid valve on the actuator chamber side of the piston acts as a bleed off for the air being fed from an upstream tap of the valve housing. This air is fed through the-hollow piston actuator shaft to the top side of the piston where it is bled off as long as the solenoid is de-energized. Energizing the solenoid closes off the actuator chamber bleed, and pressure builds up. This force overcomes spring tension and the valve opens. Any loss of pneumatic or electrical power to the valve will cause it to assume a closed position. CHARGING VALVES.- There are four backseating charging valves in the vapor cycle system- three in the evaporator group, and one in the condenser group. The valves are used to facilitate servicing of the system as one complete unit or servicing of the evaporator group or condenser group as individual units. The condenser and evaporator group assemblies are equipped with quick-disconnect refrigerant lines to allow their removal from the aircraft without a loss of refrigerant. PURGE VALVES.- The refrigerant system is equipped with two purge valves- one at the evaporator group assembly high point and the other on the condenser in the top scoop of the aircraft. The valves are similar to the charge valves. They are used to bleed the system, when required, and for attaching test equipment or the vacuum pump for system evacuation.
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